Frozen nitrogen tetroxide-hydrocarbon explosives



Aug. :21, 1956 D. ROSS ET AL FROZEN NITROGEN TETROXIDE-HYDROCARBONEXPLOSIVES Filed Aug. 14. 1951 2 Sheets-Sheet 2 DETONATOR DETONATORDETONATOR RECEPTA'CLE DETONATOR .RECEPTACLE IIIII)" 1 I I will I III! IiInlllR CONTAINER FROZEN HYDROCARBON FROZEN N 0 F IG.3..

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DOUGLAS H. ROSS THOMAS J.- McGONlGLE AT TORN EY.

FROZEN NITROGEN TETROXIDE-HYDROCARBON EXPLOSIV ES Application August 14,1951, Serial No. 241,865

4 Claims. (Cl. 102-24) This invention relates to convenient and safemeans of handling NzOi-hydrocarbon explosive mixtures and moreparticularly refers to a composition comprising frozen N204 and ahydrocarbon adapted for use as an explosive mixture.

Explosives most commonly used particularly for strip mining and quarryblasting are dynamite and blast gelatin. These explosives have thedrawbacks of being dangerous in that they are sensitive to shock; have arelatively low explosive powerabout 60% of TNT; are toxic to the personhandling them; decrease in effectiveness at lower temperatures; and arerelatively high in cost. Furthermore, the manufacture of theseexplosives requires the use of toluene or glycerine as raw materialwhich are in short supply. Because of the low explosive power ofdynamite and similar blasting powders, resort was had in a few instancesto liquid oxygen explosives but these explosives have not been widelyadopted in industry due to their hazardous nature and difliculty inhandling.

One object of the present invention is to provide an NzOi-hydrocarbonexplosive composition which is convenient and safe to use.

Another object is to provide an Nzoi-hydrocarbon explosive compositionwhich has practically zero impact sensitivity.

Another object is to provide an N2O4-hydrocarbon composition which hasan explosive power effectiveness many fold that of dynamite.

A further object is to provide an NzOi-hydrocarbon ex- ;plosivecomposition which is non-toxic during handling .by the explosiveoperator.

A still further object is to provide an Nzoi-hydrocarbcn explosivemixture which will not lose its explosive power effectiveness at lowtemperatures.

Another object is to provide an NzOi-hydrocarbon explosive compositionwhich when detonated will not generate toxic gases.

Other objects are to provide safe means and methods, i. e. freedom fromimpact sensitivity and toxicity of the explosive compositions, forhandling N2O4-hydr0carbon explosive compositions.

Further objects and advantages will be apparent from the description andaccompanying drawings.

In general the present invention is directed to compositions containingfrozen N204 and hydrocarbons and the use of such compositions asexplosive mixtures. More specifically, the present invention is directedto a composition adapted for use as an explosive mixture comprisingfrozen N204 and a hydrocarbon in the liquid or solid state. The presentinvention also contemplates a composition comprising a mixture of N204and a hydrocarbon, both frozen to a solid state.

Explosive devices adapted for use in effecting explosions in accordancewith the present invention comprise in combination a container, frozennitrogen tetroxide disposed within the container, a hydrocarbon alsodisposed within the container and a detonator attached to said containeradapted to cause explosion of the NzOi-hydrocarbon in the container.

atent 2,759,418 Patented Aug. 21, 1956 In the preferred form ofexplosive device, the container will be in the shape of a hollowcylinder open at one end containing frozen nitrogen tetroxide incylinder form and having a hollow cavity or core containing ahydrocarbon. A cap having a hollow cylinder extending therefrom forinsertion into the cavity of the frozen nitrogen tetroxide closes theopen end of the container, and a detonator adapted for causing explosionof the nitrogen tetroxidehydrocarbon in the container, is disposed inthe hollow cylinder attached to the cap.

In another form of explosive device the container may be loaded withalternate layers of frozen nitrogen tetroxide and frozen hydrocarbon inthe form of cylinders or wafers. If it is desired to prevent intimatecontact of frozen nitrogen tetroxide with frozen or liquid hydrocarbons,the frozen constituents may be covered with reasonably imperviousmaterial, i. e. paper, wax or other protective coating. The coveringshould be of a type and applied to allow the constituents to mix readilywhen both become liquid.

in another form of explosive device the container may be loaded with anintimate mixture of nitrogen tetroxide and hydrocarbon, both frozen to asolid state.

Our preferred method for preparing and exploding composition of thepresent invention comprises disposing frozen N204 and a hydrocarbon in acontainer, maintaining the N204 in solid form until it is desired toexplode the composition, thereupon melting the N204 to allow it to mixwith the hydrocarbon, and then detonating the mixture.

Although the use \of mixtures composed of liquid nitrogen tetroxide andhydrocarbon for explosives were known for some time, nevertheless thecommercial application of such mixtures is practically nil. We haveinvestigated the reasons for the noncommercial use of NzOi-hydrocarbonmixtures and found them to be primarily, difficulty in handling liquidnitrogen tetroxide explosive mixtures especially due to the effect oftoxic gases resulting from vaporization of the liquid nitrogentetroxide, and fear of detonation of mixtures of liquid nitrogentetroxide and hydrocarbon. We have obviated these difficulties byemploying nitrogen tetroxide in the frozen state thereby preventing anymaterial escape of toxic gases. Furthermore, by separately freezingnitrogen tetroxide and maintaining it in solid state separate from theliquid hydrocarbon thereby preventing mixing of the two constituentsduring handling of the composition by the operating personnel, we haveeradicated any apprehension on the part of men handling the compositionthat a premature explosion may occur. These advantages combined with thelower cost and greater explosive power of our explosive compositionstogether with other advantages enumerated herein make for a practical,cheaper, safer explosive than hitherto known.

Figure 1 is a partial section of the preferred form of assembledexplosive device showing the separate bodies of frozen nitrogentetroxide and hydrocarbon contained therein.

Figure 2 is a partial section of an alternative form of explosive deviceshowing the frozen nitrogen tetroxide in the container provided with aseries of holes for distributing the hydrocarbon throughout the body ofthe frozen nitrogen tetroxide.

Figure 3 is another form of explosive device wherein wafers of frozennitrogen tetroxide and frozen hydrocarbon are loaded interspersedly inthe container.

Figure 4 illustrates an explosive device loaded with an intimate mixtureof N204 and hydrocarbon frozen to a solid state.

Figure 5 illustrates one method of converting liquid nitrogen tetroxideas received in commercial ton containers into frozen forms for use inthe explosive deice The hydrocarbon to be employed may be anyhydrocarbon material such as derived from petroleum, coal carbonizationand distillation of shale, preferably a hydrocarbon distillate which isliquid at normal temperature and pressure. Various hydrocarbons such asbenzene, heptane and octane, as Well as hydrocarbon distillate fractionssuch as the naphthas and kerosenes, have been employed with success.tillate fractions boiling within the range of about 150- 600 F. to bemost satisfactory as one of the constituents of the N204-hydrocarbonexplosive mixture because of its lower impact sensitivity when admixedwith nitrogen tetroxide, low volatility, availability and low cost.Other fuels such as methyl alcohol and ethyl alcohol while not assatisfactory may be employed as the hydrocarbon constituent of theN204-hydrocarbon composition. Methyl alcohol may be used as a fuel to beinjected into a rocket motor containing frozen N204.

Referring to Fig. l of the drawing the explosive device shown therein iscomposed of a cylindrical rigid container 1 constructed of metal, paper,plastic or the like, enclosed at its open end by cap 2, which latter hasa small hollow cylinder 3 for use as a detonator receptacle extendingdown into the container, and a plug 4 approximately the. diameter of thehydrocarbon cavity in the frozen nitrogen tetroxide. It is not necessaryto seal container 1 with cap 2 in such manner as to prevent any escapeof gas. Desirably a small vent may be in the cap to permit leakage ofevolved vapor. In case of misfire such vent would permit release of N204rendering the residual material in the container incapable of explosion.Disposed in container 1 is a solid cylinder 5 of frozen N204 having ahollow core 6 designated hydrocarbon cavity into which hydrocarbon ispoured. A detonator 7 of any conventional type such as mercury fulminatehaving wires attached thereto is inserted in detonator receptacle 3.

The proportion of hydrocarbon to N204 may vary from about 10-35%hydrocarbon to 90-65% N204 by weight depending to a, large extent uponthe nature of the hydrocarbon employed. For maximum efliciency it wouldappear desirable to employ the hydrocarbon-N204 in stoichiometricproportion. However, we have found that a hydrocarbonrN204 mixture ismore sensitive to im pact when in stoichiometric ratio. Further we notedthat when the amount of hydrocarbon is in excess of the stoichiometricamount required for combustion with N204, the gases liberated as aresult of an explosion of such: mixture contained carbon, monoxide whichis toxic in nature. Our experiments have shown that hydrocarbon-N204compositions employing N204 in slight stoichiometric excess, roughlyabout 5%, have less impact sensitivity and generate gases when explodedconsisting essentially of C02, N2, and H20 with practically negligibleor zero amount of CO. In practice we have successfully explodedcompositions of nitrogen tetroxide with the followinghydrocarbonsoctane, heptane, benzene, petroleum naphtha boiling in; therange of 150 F. to 450 F., kerosene boiling within the range of 250 F.and 500 R, such. compositions having the following respectiveproportions of N204 to hydrocarbon by weight- 84:16, 83.5:16.5, 83:17,84:16, 84.52155.

Figure 2 represents another form of explosive device consisting ofcontainer 8 sealed at its open end by cap 9 which latter has a detonatorreceptacle 11 extending from cap 9 into the body of container 8 for thepurpose of holding detonator 12 having wires 13; attached thereto toinitiate the explosion. Disposed in container 8 is a solid cylinder 14of frozen nitrogen tetroxide provided with a plurality of holes 15 inthe frozen nitrogen tetroxide which will keep the liquid hydrocarbonpoured therein separate until such time as the nitrogen tetroxide ispermitted to melt thereby forming the explosive mixture.

Another method of carrying out this invention involves freezing thenitrogen tetroxide and the, hydrocarbon separately in the form ofcylinders or wafers which can: be

We have found petroleum dis 4 loaded alternately to provide the properratio of hydrocarbon to oxidizer, which upon melting will properly blendinto the desired explosive mixture. As shown in Fig. 3 layers 16 offrozen N204 are separated by layers 17 of frozen hydrocarbon incontainer 18. If desired intimate contact between the layers may beprevented while the N204-hydrocarbon is in the frozen state by placing aprotective coating 19, such as paper or wax, between layers 16 and 17,which layers 16 and 17 are desirably molded with a hollow core 21 toprovide a cavity for the insertion of detonator receptacle 22 attachedto cap 23 and also to allow the constituents to mix readily when bothbecome liquid. The usual detonator 24 provided with wires 25 fits intodetonator receptacle 22.

In the Arctic and Antarctic regions conventional types of explosivessuch as dynamite and nitroglycerine lose much of their explosivestrength or fail completely at the low temperature conditions prevailingin these regions. Accidents have been known to occur due to an operatorattempting to warm frozen dynamite prior to use. We have discovered thatan intimate mixture of N204-hydrocarbon frozen to a solid state willexplode when detonated without any noticeable loss in explosive power ascompared with a mixture of liquid N204-hydrocarbon. Further the impactsensitivity of a frozen mixture of N2O4-hydrocarbon is low and may besafely handled by an operator.

Figure 4 illustrates an explosive device composed of container 26 intowhich is placed a solid cylinder 27 of a frozen intimate mixture of N204and hydrocarbon with a hollow core in cylinder 27 adapted to receivedetonator receptacle 28 attached to cap 29 sealing open end of container26. Into detonator receptacle 28 is inserted detonator 30 having wires31 attached thereto.

Figure 5 diagrammatically illustrates one practical method of preparingfrozen nitrogen tetroxide in form suitable for use in an explosivecontainer at the situs such as a coal mine or quarry where explosivesare used. Liquid nitrogen tetroxide is shipped in commerce on railroadcars in large, strong metal vessels 32 termed in the industry as toncontainers." The liquid nitrogen tetroxide is withdrawn from toncontainer 32 through line 33 and valve 34 and discharged into enclosedcooling tank 35 wherein the temperature is maintained at about 10 C. bypassing a refrigerant through refrigerating coil 36 immersed in theliquid N204 contained in cooling tank 35. When it is desired to preparecylinders of frozen N204, liquid N204 is passed through line 37 andvalve 38 into mold 39 of a form suitable to produce the desired shape ofN204, suspended by means of bracket 41 on molding tank 42. Liquidrefrigerant, such as brine, enters tank 42 through line 43, circulatesaround mold 34 thereby freezing the liquid nitrogen tetroxide containedtherein, i. e. cools it to a temperature below about l0 C., anddischarges from tank 42 through line 44. Although only a single mold 32is shown in the drawing, obviously a plurality of molds may be employedin tank 42. The frozen cylinder 45 of N204 may be removed from mold 39placed in a container similar to that shown in Figure 1 and then placedin a conventional storage refrigerator, not shown in the drawing,wherein a ready supply of containers with frozen liquid nitrogentetroxide may be kept for use. Hydrocarbon such as kerosene may beseparately stored in a tank not shown in the drawing as the source ofhydrocarbon supply for filling the hydrocarbon cavity in the explosivedevices illustrated in Figures 1 and 2.

From the foregoing it will be evident that a large magazine ofexplosives such as dynamite with its attendant hazard is. eliminated bythe practice of this invention in that. nitrogen tetroxide andhydrocarbon are maintained separately until shortly before use and thenonly placed together in very small quantities in the container. In thisconnection it should be noted that it is. not uncommon for a single coalmine to consume about 200 tons ofexplosive per month.

In strip mining, a series of holes are drilled in the ground with thesize of the holes depending upon the contour of the surface and thenature of the rock formation, and in these holes a conventionalexplosive such as dynamite is placed, which operation is called loading;the top of the hole plugged up with loose earth termed stemming, and thedynamite then detonated to break up the surface overlaying the coal.Since dynamite or other conventional explosive powders used for the samepurpose constitute a preformed mixture susceptible of explosion, itpresents a real hazard during the carrying of the dynamite to the holeinto which it is to be placed and particularly during the loading periodwhen the dynamite is dropped in the hole. In contrast the explosivedevice as illustrated in Figures 1, 2 and 3 contains a non-explosivecomposition during the carrying to and placing in the hole of theexplosive device by the operator because the nitrogen tetroxide is infrozen condition and in that form does not admix with the hydrocarbon inthe container of the explosive device. After the explosive devicescontaining frozen N2O4-hydr0carbon are placed in the holes of the minethe operators move to a place of safety and after waiting for a periodof about to minutes to permit the frozen nitrogen tetroxide in theexplosive device to melt due to the heat of the surrounding atmosphereand thereby cause it to blend with the hydrocarbon, the explosive isthen detonated.

As pointed out previously the use of an explosive device containingfrozen nitrogen tetroxide-hydrocarbon in accordance with the presentinvention has the advantages as compared to conventional explosives ofgreater safety, lower cost and reduced toxic effects with respect toboth toxic effects resulting from handling the explosive and from thegases generated by explosion of the explosive. Perhaps, an even greateradvantage in monetary terms results from the greater effectiveness ofNzOi-hydrocarbon as compared with conventional explosives. In fieldtests one pound of dynamite was required to disrupt one cubic yard ofrock overburden. In a similar test one pound N204-k6IOSCl16 inaccordance with the present invention disrupted 5 cubic yards of rockoverburden. A very large item of expense in strip mining is the cost ofdrilling holes for loading With explosive. As is evident the number orsize, or both, of such holes which need be drilled is materially reducedwhen employing NzOr-hydrocarbon as compared to use of conventionalexplosives thereby effecting a saving in money and speeding up ofoperation.

Example 1 .lnto a cylindrical container as illustrated in Figure 1having a diameter of about 2 inches and about 6 inches high was placed asolid cylinder of frozen N204 having approximately the same internaldiameter and height of the container and having a hollow core, thecavity of which was equal to about of the volume of frozen N204cylinder. Kerosene is poured into the cavity and the container sealedwith a cap which has a detonator receptacle extending into the core ofthe frozen N204. The amount of N204 in the container was approximately4% in stoichiometric excess of the kerosene. A detonator was placed intothe detonator receptacle and the explosive device permitted to stand for15 minutes to allow the frozen N204 to melt and blend with the kerosene.An electric current was passed to the detonator which caused animmediate explosion.

Similar explosive devices employing benzene, heptane and octane as thehydrocarbon constituent were prepared and exploded in the same manner.Tests were made to determine the explosive power in accordance with theballistic mortar test employed by the Bureau of Mines on these variouscompositions. The explosive mixtures tested were found to have 160-190%the explosive power of TNT as measured by the ballistic mortar method.When compared to dynamite which has only 60% the explosive power of TNT,the N2O4-hydr0carbon mixtures were 6 about three times as effectivebased on the ballistic mortar tests.

The N2O4-hydrocarbon compositions were also subjected to impactsensitivity tests by dropping weights on compositions from varyingheights. The results of these tests show the compositions to beinsensitive to impact for all practical purposes.

Example 2 Liquid N204 and benzene in the proportion of 83:17% by weightwere intimately mixed and frozen in the form of a solid cylinder andthen placed in a container as. shown in Figure 4. The frozen mixtureupon detonation exploded immediately. The explosive force resulting fromexplosion of the frozen mixture was found to be substantially the sameas a mixture of liquid N2O4-hydrocarbon in the same weight proportion.

Although certain preferred embodiments of the invention have beendisclosed for purposes of illustration, it will be evident that variouschanges and modifications may be made therein without departing from thescope and spirit of the invention.

We claim:

1. A method of mine blasting which comprises boring a hole in the solidcomposite to be blasted, placing in said hole a device comprising anunpartitioned container containing a frozen body of nitrogen tetroxideand a separate body of hydrocarbon wherein upon melting of the nitrogentetroxide the nitrogen tetroxide will blend with the hydrocarbon, saiddevice also having a detonator adapted to cause explosion of thenitrogen tetroxide-hydrocarbon in the container, thereafter melting thenitrogen tetroxide to allow it to mix with the hydrocarbon, and thendetonating the mixture of nitrogen tetroxide and hydrocarbon.

2. A method of mine blasting which comprises boring a hole in the solidcomposite to be blasted, placing in said hole a device comprising anunpartitioned container containing a body of hydrocarbon and a separatefrozen body of nitrogen tetroxide in slight stoichiometric excesswherein upon melting of the nitrogen tetroxide the nitrogen tetroxidewill blend with the hydrocarbon, said device also having a detonatoradapted to cause explosion of the nitrogen tetroxide-hydrocarbon in thecontainer, thereafter melting the nitrogen tetroxide to allow it to mixwith the hydrocarbon, and then detonating the mixture of nitrogentetroxide and hydrocarbon.

3. A method of mine blasting which comprises boring a hole in the solidcomposite to be blasted, placing in said hole a device comprising anunpartitioned container containing an intimate mixture of frozennitrogen tetroxide and a frozen normally liquid combustible fuel, saiddevice also having a detonator adapted to cause explosion of thenitrogen tetroxide-combustible fuel in the con-- tainer, and thendetonating the mixture of nitrogen tetroxide and combustible fuel.

4. A method of mine blasting which comprises boring; a hole in the solidcomposite to be blasted, placing in said hole a device comprising anunpartitioned container containing an intimate mixture of frozennitrogen tetroX-- ide and a frozen hydrocarbon distillate boiling withintherange of -600 F., said device also having a detona-- tor adapted tocause explosion of the nitrogen tetroxide-- hydrocarbon in thecontainer, and then detonating the: mixture of nitrogen tetroxide andcombustible fuel.

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6 n am 0 Beth Chem. Abstracts, vol. 18 1924: 1 242 9.

OTHER REFERENCES Schaarschmidt: Chem. Abstracts, v01. 19 1925 p.

Fierz: Chem. Abstracts, v01. 16 (1922), p. 1868. 5 942.

1. A METHOD OF MINE BLASTING WHICH COMPRISES BORING A HOLE IN THE SOLIDCOMPOSITE TO BE BLASTED, PLACING IN SAID HOLE A DEVICE COMPRISING ANUNPARTITIONED CONTAINER CONTAINING A FROZEN BODY OF NITROGEN TETROXIDEAND A SEPARATE BODY OF HYDROCARBON WHEREIN UPON MELTING OF THE NITROGENTETROXIDE THE NITROGEN TETROXIDE WILL BLEND WITH THE HYDROCARBON, SAIDDEVICE ALSO HAVING A DETONATOR ADAPTED TO CAUSE EXPLOSION OF THENITROGEN TETROXIDE-HYDROCARBON IN THE CONTAINER, THEREAFTER MELTING THENITRO-